Agricultural machines, such as self-propelled agricultural sprayers, may provide conventional two-wheel steering or four-wheel steering options. In a conventional two-wheel steering configuration, a machine may be steered left or right via two or more wheels in the front, while two or more wheels in the rear of the machine are held in a substantially straight direction with respect to the machine. In a four-wheel steering configuration, the machine may be steered left or right via wheels in the front and rear both turning. For example, to turn left, wheels in the front may turn left while wheels in the rear turn right, and to turn right, wheels in the front may turn right while wheels in the rear turn left.
Agricultural machines may also provide automatic steering in addition to conventional steering. Automatic steering may allow an onboard computer system to control steering of the sprayer according to a predetermined travel plan. Although both four-wheel steering and automatic steering are beneficial, it is typically desirable to deactivate four-wheel steering when automatic steering is enabled. That is because four-wheel steering provides a relatively large steering response for a given steering input, which can make automatic steering more difficult.
At certain times, operators may want to take over manual steering control and disengage automatic steering. When this happens, the operators may want to activate four-wheel steering, such as one when making tight turns in the headlands of fields. However, this can require a lot of control manipulation by the operator to engage and disengage four-wheel steering when switching to manual steering, thereby increasing complexity and susceptibility to error. It is therefore desirable to provide a system which simplifies operation of the machine while eliminating one or more of the foregoing disadvantages.